Describes Fuel/Cargo Containers that can hold cargo, or be used to hold fuel. The containers take up an extra 5 percent of space for the piping.

Question: Can the fuel in the containers be used in a Jump, like Demountable tanks? Or do they have to be pumped into a fuel tank for use separately from the container, like the collapsible bladder?

"Containers of this sort are sometimes used aboard
converted merchant craft to support other exploration
ships by acting as tankers or long-range supply ships.
They also increase the capabilities of an ordinary
merchant, permitting extended transits between mains
and clusters when necessary, yet retaining almost all
capacity for day-to-day freighting operations."

I am leaning towards the usable during Jump for a couple of reasons.
1: The cost: 5 times that of Demountable tanks. If they were not better than Demountable tanks, why the big increase in cost?
2: The extra space. The tankage ends up taking up 5 percent extra space for the permanent piping. This piping could be connected to the fuel tank or Jump engine, so why not give it the usage for the Jump engine.

This offers an incedibly flexible arrangement, for the loss of 5 percent of the cargo space. I think there will be a rough draft of a Deep space cargo craft without fuel tanks showing up in an hour or so.

If you look at the Armstrong class ship from page 36 of the book it has 534 tons of fuel space. This gives 2 Jump 3 and 32 weeks of operation. The ship also has 95 tons of cargo space.
If you converted that space into Cargo/Fuel Containers you would get 599 tons of fuel capacity and 6228.95 tons of cargo used up. You lose 30 tons of space in the conversion.
This costs 3 Million Credits.

What you gain is the ability to fuel the ship for the job at hand and store cargo for whatever space you have left. If you are crossing a rift and want extra capacity, cut back on cargo and fill the tanks to the gills.
If you are in a local area and do not need a 6 Hex reach, store less fuel and load up on cargo.
This also offers the ability to stay on station a really long time.

The 5% space is more likely due to the need to make the containers insulated to store liquid hydrogen rather than piping. A square tank in real life isn't as effecient as one that is built with rounded portions to ensure the liquid drains properly, but that's a factoid that could be overlooked.

The tanks could also simply store water, which would make it far easier to drain and then run through a purifier to convert to Lhyd. It would be cheaper and safer since H20 requires no special handling.

But that would certainly exclude the containers from being considered truly tied into the fuel system. With multiple containers involved I'd say they could be considered fuel tanks (after running the water through processors) but not demountable ones. It would also make it more likely for them to be drained and then turned into cargo - you'd just need to air blast them out to dry for some cargos - other you could stuff in them while they are wet with no worry.

great rift adventure 1: islands in the rift has a ship that uses them. Unfortunately (for this discussion) it’s a jump-1 ship, so in this case it doesn’t matter how they work, but the info text had this:

Rather than using collapsible fuel bladders or demountable tanks, Perfect Stranger has been reftted to switch between fuel or cargo in a few hours. This requires little more than fushing out the tanks to ensure no liquid hydrogen remains, then loading them up with cargo as needed

This could mean that the only real advantage is that changing between fuel and cargo is faster, but bladders already offers this functionality, and why even mention demountable tanks if they can’t compete? To be a valid alternative to both bladders and demountable tanks, I’d say it feels like it needs to be able to do the job of both. Demountable tanks can be used for jump fuel, but the process to swap between fuel and cargo is slow, whereas bladders are quick to fill or drain (easy converting between fuel or cargo) but can’t be used directly, so a third option (that’s more expensive than the others) could combine the effects of both - can be used for jumps and is quick and easy to change.

So with this change to the rules, AnotherDilbert has it right - it's a major change to the concept of shipbuilding rules. If you can do this with a cargo container then you can do it with cargo holds as well. It's just a matter of scale.

The cargo hold becomes a series of containers that can hold cargo or fuel. A J2 ship of200 tons needs 40 tons of fuel to make a jump 2. So having containers in 40 ton units allows for a Jump 2 capacity in cargo or fuel. You may want a containers in a 20 ton capacity in case you wanted to make a Jump 1, then you could fill that 20 ton container with fuel and use the 40 ton containers for cargo, maximizing profit.

It is a major shift in design for a 5% space cost. My Jump Station ship and the origami ship I have posted about looks to the issue of loss of profits when you are moving an empty fuel tank. If you could use the space for cargo instead of fuel you could make a lot more money.

Instead of 42000 Dt jump fuel tanks it has 44211 Dt Fuel/Cargo Containers, still allowing J-4.
In peacetime it can use a 35 kDt drop tank and still be capable of J-3. That would leave it with 35 000 Dt cargo capacity.

At a cost of 2.2 kDt bigger fuel tanks and insignificant money. We could do the same with a 35 kDt module at no cost in size but a cost of MCr 3000. We could get the 2.2 kDt back by making the ship a little bigger at the cost of a few billion. So, the options are about equal...

Nice work AnotherDilbert! That shows the improved logistics when you are not carting around an empty tank.

My example is much smaller. Look at pg 119 of High Guard and the A2 Far Trader.

If one of the fuel tanks was converted into fuel/cargo space it would take 21 tons of space and cost 100 000 Credits. So you lose 1 ton of the regular cargo area and gain 20 tons of fuel/cargo space in the former fuel tank area.

So now on a Jump 1 job you can fit 83 tons of cargo, offering a 20 000 Credit extra income for the Jump 1 job. 5 trips and the improvement has paid for itself.

If you skipped the drop tank and went with 2 dedicated fuel tanks. One tank with the 4 or 8 weeks of Power Plant fuel, and a fuel tank for Jump 1 operations, the rest of the former fuel tankage could be converted into cargo/fuel containers. The base Jump 1 tankage you can leave alone because the shortest Jump you will make is Jump 1, why pay 5 percent extra space for something you will always use in a Jump. It is the rest of the fuel space you want to increase profits on.

If you are using Drop Tanks then by all means maximize cargo capacity. Think about what that 35 000 tons of cargo could mean for a battle. Spare parts, equipment, rations, medical supplies and whatever else you need to bring along.

A drawback/risk is that if the ships needs to leave quickly it needs to unload the containers of the 35 000 tons of supplies and then refill the containers with fuel before it can Jump again, but the ability to bring a load of supplies with you and reduce your supply line demand even for a first step is pretty important.